Add arb_checkPublisherHealth method

[PlasmaPower]

Also enables the arb namespace by default, and moves the revalidate block API to arbdebug.

[codecov]

Codecov Report

Merging #898 (e3d01f5) into master (686b037) will decrease coverage by 4.30%.
The diff coverage is 33.33%.

❗ Current head e3d01f5 differs from pull request most recent head c3b2c0e. Consider uploading reports for the commit c3b2c0e to get more accurate results

@@            Coverage Diff             @@
##           master     #898      +/-   ##
==========================================
- Coverage   51.81%   47.50%   -4.31%     
==========================================
  Files         228      216      -12     
  Lines       28371    24282    -4089     
  Branches      502      502              
==========================================
- Hits        14701    11536    -3165     
+ Misses      12101    11169     -932     
- Partials     1569     1577       +8     

[hkalodner]

LGTM